Examples of a projection video display device (projector device) of the related art are disclosed in Patent Documents 1 to 3. In the projector devices disclosed in the Patent Documents, a mirror of which the back side is substantially plate-shaped is installed on the top surface of the devices in an openable manner. When the projector device is in use, the mirror is opened, and an image is projected in a direction which is different in angle from the mirror surface. When the projector device is not in use, the mirror is closed, a substantially flat surface is formed on the top surface of the projector device. In the projector devices disclosed in Patent Documents 2 and 3, opening and closing of the mirror is automatized by using a driving motor.